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SubjectRe: [RFC] Fix 2.6.33 x86 regression to kgdb hw breakpoints - due to perf API changes

* Jason Wessel <jason.wessel@windriver.com> wrote:

> I'll lead with a question. Are the people making the Perf API changes
> booting allyesconfig kernels?
>
> The regression tests built into the kernel for kgdb fail as a result
> of the perf API changes and can result in a hard kernel hang.
>
> My hope would have been that someone would have reported the problem,
> created a patch to disable the test that hangs the kernel, or to fix
> kgdb such that it works with the API changes. Likewise, if there are
> tests I should run to regression test the changes to the perf API, I
> would like to know since we all want to make use of the same hw
> resource.
>
> A patch has been included in this mail which allows kgdb to pass the
> internal regression tests for hw breakpoints. I would like to get
> some comments or start a discussion as to how to solve this problem in
> the 2.6.33 cycle, as it is a regression in functionality.

Hm, the kgdb hw-breakpoint changes freshly put into v2.6.33 look pretty
broken: they access the raw hw registers and ignore the higher level
abstraction. Your patch still uses way too low level primitives. Please
use the highlevel abstraction: register/unregister_wide_hw_breakpoint()
should do the trick. (if there's any changes/extensions needed to it
then please let us know about it.)

If that's too much for v2.6.33 then i guess we need to revert or disable
the kgdb hw-breakpoint changes for now.

Thanks,

Ingo


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